I wasn't successful trying to "drill out" an engine mount hole in the stress ball potato!
I can easily drill and hollow a hole in the round ball Styrofoam Sputnik model kits.
But the soft, heavy rubber potato won't fly! In this form, it won't end up being a kit.
I night do a "one-off" carving a potato out of white Styrofoam. Then I'll have to get some foam safe paints.
I haven't given up on this one, I think it'll be pretty funny.